All I had to do was stand on the platform in front of the gears (you will have had to eliminate the walking cannon). Then face the gears and use telekinesis on the 'thing jamming the gears'. Once I did that, the drawbridge came back down.

On the everything: I tried jumping/levitating and firing at it, I threw trees and objects at it by telekinisis, I tried to get on the platform by levitating all the way from the tall towers of the entrance of the castle or from the left side but it's impossible!!!

This part had some very, very colorful language coming from my innocent (heheh) little mouth.

You have to climb up the ladder, go across the tightropes. From there you'll bump into a sword with the end of the tightrope curled around it.

From there, I did a double-jump up, pushed forward, and at the same time held onto the L-trigger to float. It was annoying as hell, but i finally reached the other platform and could unstick the gears.

Didn't really think that part was a challenge. Especially since I had already cleared out the entire castle long before Napolean retreated into there. But where I do feel quite stupid is how long it took me to figure out that the champagne corks were the way out of waterloo world. I'm just glad I eventually figured it out on my own :P

Thought I would bump this back up...
You don't have to go as far around as the the vertical sword blade.
Use the ladder, double jump to the next platform. Cross the rope but don't go any further on the second rope.
From the corner where the first rope ends, face the horizontal sword (which is on the other side of the castle thingy) Levitate bounce up then PSI Float over to the horizontal sword. If you did it right, you should just grasp the edge of the sword and hang from it. You might hit the archway that's between the rope corner and the horizontal sword, but you should still be able to make it the edge of the sword. Climb up onto the horizontal sword. Don't go on the rope which leads to the vertical sword.
Instead, Levitate bouce up to the castle corner above the horizontal sword. There's a flat space up there.
Once you're on the flat area, Levitate bounce up over the roof and you should land in the center of the castle/drawbridge area. From there you can bounce up to either side of the castle thingy and Levitate bounce up and PSI float to either free-standing tower. One tower has a helmet power up (for health) and from the other tower you can TK/move the thing jamming the gear.